Composite dipole arrays are known. A composite dipole array can contain a string of alternating resonant circuits whose function is to receive electromagnetic radiation at two different frequencies and then re-radiate a single signal at the difference frequency. Re-radiation at the difference frequency is facilitated by non-linear device elements of the composite dipole array.
For example, such composite dipole arrays can covert energy from a pair of higher frequency microwave signals into a lower frequency signal at the difference frequency of the two higher frequency signals.
Composite dipole arrays can provide frequency conversion for a variety of applications such as remote sensing, short range covert communications, compact radar ranging systems, inter-satellite communication links, testing of integrated circuits, and even medical imaging and treatment. In the field of medical imaging, for example, tumors and other pathologies can be identified and characterized.
Examples of composite dipole arrays structures are described in U.S. Pat. No. 6,999,041, entitled Dual Frequency Antennas And Associated Down-Conversion Method, issued Feb. 14, 2006, and in U.S. Pat. No. 7,009,575 entitled High-Frequency Two-Dimensional Antenna and Associated Down-Conversion Method, issued on Mar. 7, 2006, the entire contents of both of which are expressly incorporated herein by reference in their entirety.
However, the ability of a contemporary composite dipole array receiver to detect incident electromagnetic radiation is limited by the power of the incident signal, the sensitivity of the receiver, and the gain of the antenna. Of course, the range of a composite dipole array receiver is dependent upon its ability to detect incident electromagnetic radiation.
In some instances, the ability to detect incident electromagnet radiation can be improved by increasing transmitted power, but this is not always possible. Increasing the transmitted power can raise cost and safety issues. In some applications, transmitted power may not be under the control of the user.
Additionally, the ability to detect incident electromagnet radiation can be improved by increasing receiver sensitivity. However, when a low noise receiver is being used, little improvement is generally available in the area of receiver sensitivity.
As a result, there is a need for increasing the gain of a contemporary composite dipole array antenna so as to enhance a receiver's ability detect incident electromagnetic radiation and thus to enhance the range of the receiver.